Making Sense of Results: Measures of Effectiveness in Randomised Controlled Trials
In this module, we look at the main measures of effectiveness used to report the results of randomised controlled trials: absolute and relative risk, odds, and the number needed to treat or harm. In addition, we outline the importance of confidence intervals (CIs) and P values not only to critical appraisal but also when making your individual judgements about whether the results of published research demonstrate an effect that would be of more benefit than harm to your local population.
Using the CASP Statistics Workbook and published data from a randomised controlled trial (NB: it is the same trial that we featured in the “How to use a CASP randomised controlled trial checklist” module), to practice how to calculate the odds ratio, the risk ratio, relative risk reduction, absolute risk reduction and the number needed to treat.
Erica Ison is the lead for the Critical Appraisal Skills Programme at the Oxford Centre for Triple Value Healthcare. She is an experienced trainer/facilitator in a range of fields and has worked with a variety of people from health and care professionals and third sector personnel to politicians, students and members of the public.
Erica also designs and develops training and skills development courses, tailored for local, national and international audiences. Erica is an Expert Adviser to the World Health Organization European Network of Healthy Cities, and one of her main responsibilities is training and skills development. Erica also worked on the European Union’s Equity Action programme training civil servants in assessing the impact of government policies on equity.